Critical achievements in mental representation are occurring during the first few years of a child's life, but behavioral indicators of conceptual development have often required capacities that confound retrievel and other production limitations. In this proposal three experiments are outlined to test the feasibility of using a well-organized response in very young children, their looking behavior, in controlled experimental settings to make inferences about the development of conceptual knowledge. The three experiments are designed for one-year-olds to test language comprehension, to test semantic memory for features and elements of the home environment, and to test the hypothesis that the function of stimuli significantly contributes to early concept knowledge. These three experiments have been selected to help determine the range and kinds of problems that can be addressed using systematic recording of looking behavior in one-year-olds and to clarify the possible limitations, both methodological and theoretical, associated with the use of such a measure to learn more about early conceptual knowledge.